Un cuento árabe y un milagro de Berceo

Sin resume

"El amor hace sutil al hombre". Ibn Hazm de Córdoba y la tradición románica.

Sin resume

Pig slurry incorporation with tillage does not reduce short-term soil CO2 fluxes

Tillage and organic fertilization impact short-term soil CO2 fluxes. However, the interactive effect of these two management practices has been rarely studied under field conditions. The objective of this study was to evaluate the impact of tillage (NT, no-tillage, and CT, conventional tillage) and fertilization strategy (PS, pig slurry, and MF, mineral fertilizer) on short-term soil CO2 fluxes in a rainfed Mediterranean agroecosystem. Soil CO2 fluxes were measured several times during two tillage and pre-sowing fertilization periods in 2012 and 2013 (7 and 6 times in 2012 and 2013, respectively). In the two years studied, tillage and fertilization significantly affected soil CO2 fluxes, but the interaction between both factors was not significant. The application of PS resulted in a sharp and immediate increase in the soil CO2 flux. One hour after the application of the organic fertilizer, soil CO2 emissions increased from 0.05 to 0.70 g CO2 m−2 h−1 and from 0.08 to 0.82 g CO2 m−2 h−1 in 2012 and 2013, respectively. Unlike fertilization, 1 h after tillage similar soil CO2 fluxes were observed in CT and NT plots. However, after 7 h, larger fluxes were observed in CT compared with NT in both years. Cumulative CO2 flux during the first 24 h after fertilization and tillage was about three- and two-fold greater in PS than in MF and in CT than in NT, respectively. The results of this study showed that in rainfed Mediterranean systems, soil management and fertilization have a noteworthy impact on short-term soil CO2 losses though no interactive effects were observed between both management practices.This research was supported by the Ministry of Economy and Competitiveness of Spain (AGL2010-22050-C03-01/02; AGL2013-49062- C4-4-R) and the COMET-Global project (FACCE-JPI grant)

Drag coefficient for irregularly shaped grains: rotational dependence at high Reynolds numbers

The nature and behaviour of the drag coefficient of irregularly shaped grains within a wide range of Reynolds numbers is discussed. Using computational fluid dynamics (CFD) tools, the behaviour of the boundary layer at high Re has been determined by applying the Reynolds Averaged Navier-Stokes turbulence model (RANS). The dependence of the mesh size and the grid resolution in the modelling are validated with the previous experimental results applied in flow around isolated smooth spheres. The drag coefficient for irregularly shaped grains is shown to be higher than that for spherical shapes, also showing a strong drop in its value at high Re (drag crisis) but lower than that of the sphere. The influence of the angle of incidence of the flow with respect to the particle is analysed, where our findings show an interesting oscillatory behaviour of the drag coefficient as a function of the angle of incidence, fitting the results to a sine-squared interpolation, predicted for particles within the Stokes' laminar regime and for bodies with an ellipsoidal shape (elongated and flattened spheroids) up to Re=2000. The statistical analysis shows a Weibullian behaviour of the drag coefficient when random polar and azimuthal rotation angles are considered.Comment: 14 page

Remesas personales desde y hacia Chile

Globalization, which involves progressive integration of countries’ economies, has resulted in an increasing number of people moving from one country to another, without losing their ties to their original home economies. Increasingly, immigrants are sending money to their home countries (remittances). These remittances have raised great interest in developing countries, not only because of their signifi cant volume and impact on local economies, but also because of their potential effects on the fi nancial system and on economic development and growth. Chile has not escaped this phenomenon. Although it has not reached levels comparable to those of other Latin American economies, growing immigration from neighboring countries and the emigration process that occurred in past decades have made it necessary to investigate the issue and to measure Chile’s remittance fl ows to and from other countries. This document presents the concept of remittances and classifi cations according to international defi nitions by institutions focused on the subject, such as the World Bank, the CEMLA, the International Monetary Fund and the Group of Luxembourg. It then analyzes the mechanisms of remittance transfers currently used in the world and international experiences regarding sources and estimation methods. The main characteristics of this market in Chile are also shown. Finally, it shows the main results of the surveys carried out yearly between 2007 and 2010. These surveys were applied to money transfer companies working in Chile, which provided information about the transactions made in the period 2005-2009.

Desigualdad del ingreso en la República Dominicana 2012-2019: resumen metodológico y resultados comparados

En este documento se presenta una revisión de las estadísticas distributivas en la República Dominicana a partir de la combinación de distintas fuentes de información: encuestas de hogares, registros tributarios y cuentas nacionales. Es un complemento del informe técnico “Desigualdad del ingreso en la República Dominicana 2012-2019: una revisión a partir de la combinación de fuentes de datos”, y tiene el propósito de difundir a un público más amplio las principales características de la metodología, así como de presentar un resumen de los resultados obtenidos para la República Dominicana en el contexto regional. La metodología y resultados presentados en este documento constituyen un paso importante hacia una mayor disponibilidad de información para la medición y el análisis de la desigualdad, y sus resultados permiten tener una mirada más completa de las brechas de ingreso de la sociedad dominicana.Resumen .-- Introducción. A. La relevancia de la desigualdad del ingreso en América Latina y el Caribe. B. Hacia mediciones complementarias de la desigualdad en República Dominicana .-- I. Metodología para medir la desigualdad del ingreso mediante la combinación de fuentes de información .-- II. Nuevos resultados sobre la desigualdad del ingreso en la República Dominicana .-- III. Conclusiones

Simulating climate change and land use effects on soil nitrous oxide emissions in Mediterranean conditions using the Daycent model

In Mediterranean agroecosystems, limited information exists about possible impacts of climate change on soil N2O emissions under different land uses. This paper presents a modelling study with a dual objective. Firstly, the biogeochemical Daycent model was evaluated to predict soil N2O emissions in different land uses in a typical Mediterranean agroecosystem. Secondly, the study aimed to determine the impact of climate change on soil N2O emissions in different Mediterranean land uses over an 85-year period. Soil N2O emissions were measured in three land uses (cropland, abandoned land and afforested land) over 18 months (December 2011 to June 2013) in a characteristic Mediterranean site in Spain. For climate change simulations, Daycent was run with and without atmospheric CO2 enrichment using climate data from the CGCM2-A2 model. The cumulative N2O emissions predicted by the Daycent model agreed well with the observed values. The lack of fit (LOFIT) and the relative error (E) statistics determined that the model error was not greater than the error in the measurements and that the bias in the simulation values was lower than the 95% confidence interval of the measurements. For the different land uses and climate scenarios, annual cumulative N2O emissions ranged from 126 to 642 g N2O-N ha−1 yr−1. Over the simulated 85-year period, climate change decreased soil N2O emissions in all three land uses. At the same time, under climate change, water filled pore space (WFPS) values decreased between 4% and 15% depending on the land use and climate change scenario considered. This study demonstrated the ability of the Daycent model to simulate soil N2O emissions in different land uses. According to model predictions, in Mediterranean conditions, climate change would lead to reduced N2O emissions in a range of land uses.Jorge Álvaro-Fuentes acknowledges the receipt of a fellowship from the OECD Co-operative Research Programme: Biological Resource Management in Sustainable Agricultural Systems in 2013. Daniel Plaza-Bonilla received a “Juan de la Cierva” grant from the Ministerio de Economía y Competitividad of Spain. This study was also possible through funds provided by the Aragon Regional Government and La Caixa (grant GA-LC-050/2011), the Ministry of Economy and Competitiveness of Spain (grant AGL2013-49062-C4-4-R) and the COMET-Global project (FACCE-JPI grant). We are grateful to María José Salvador and Javier Bareche for laboratory assistance

Eficacia en la resolución de problemas de optimización por estudiantes de ingenieria

Se presenta un estudio sobre la eficacia que muestran estudiantes de ingeniería en la resolución de problemas de optimización. Se seleccionaron y se aplicaron a estudiantes de ingeniería de una universidad del noroeste de México, problemas con enunciado del texto escolar que se utiliza en la clase de Cálculo. Escribieron sus respuestas y se les solicitó externaran en voz alta sus pensamientos, mismos que fueron grabados y transcritos. El análisis tanto de la práctica escrita como de la transcripción se llevó a cabo mediante herramientas suministradas por el Enfoque Ontológico-Semiótico y algunos elementos de Metacognición. Los hallazgos sugieren que para tener eficacia en la resolución de problemas matemáticos en optimización se requiere tener una adecuada comprensión de los objetos intervinientes y una buena gestión metacognitiva del proceso de resolución

La ontosemiótica y la ecología de significados que desarrollan los estudiantes de ingeniería al resolver problemas con ecuaciones diferenciales de primer orden

Se desarrolla una investigación que tiene como objetivo central caracterizar los objetos matemáticos previos necesarios para que el estudiante de ingeniería pueda abordar una gama de problemas que se resuelven utilizando ecuaciones diferenciales de primer orden. En este trabajo se presenta un análisis ecológico utilizando algunas herramientas teóricas del enfoque ontosemiótico de la cognición matemática (Godino, 2003), a fin de indagar cuales son los significados institucionales de los objetos matemáticos, cuáles son las relaciones implícitas y explicitas de los elementos y los significados que se ponen en juego cuando los estudiantes de ingeniería se enfrentan a la resolución de éstos problemas. El análisis tiene como propósito caracterizar la complejidad ontosemiótica de problemas de libros de texto y los conflictos potenciales que puedan producirse en los estudiantes del curso de Ecuaciones Diferenciales en la Facultad de Ingeniería de la Universidad Autónoma de Baja California, México